The paper presents a new gate matrix layout system:GMS for VLSI CMOS circuits.GMS can be used as a cell generator to produce basic cells automatically.The whole layout procedures in GMS are divided into gate assignment

net assignment and compaction. Based on the consideration of many practical constraints

GMS uses a new gate assignment algorithm which can improve Li’s algorithm[6] a lot.GMS also transfers net assignment into an extended l-dimensional assignment problem

and a heuristic algorithm is developed. GMS allows users to do interactive improvement on the layout results.It compacts the layout results to further reduce the used area.GMS has been implemented in C language on Micro VaxII.Many practical examples are tested and the experimental results are promising.